PCR is a powerful technique that has been used widely in the diagnosis of HIV infections. PCR based diagnostic techniques have primarily focused on HIV-1 as it is the type prevalent in the US, the western hemisphere and most of Africa. However, AIDS cases due to HIV-2 infection are consistently on the rise, especially in West Africa and many less developed countries, making it necessary to develop PCR assays to detect HIV-2 strains. There have been several PCR assays designed to fulfill this requirement. As all the PCRs reported to date are specific either for HIV-1 or HIV-2, a clinical evaluation in a population with significant numbers of infections due to HIV-1, HIV-2 or both viruses would require the use of both assays. In order to circumvent this double test approach, we designed PCRs so that a single assay would be able to differentiate between both viruses by giving different amplification signals. We selected gag, pol and LTR regions for this purpose and presently are in the process of optimizing the assays. These primers will be used in clinical evaluation studies on samples collected from different geographical regions. They will also be used in viral infection studies as well.